A roll forming apparatus is known as an apparatus for manufacturing a sectionally L-shaped long plate member as shown in FIG. 8 or a sectionally U-shaped long plate member as shown in FIG. 9. FIGS. 13A to 13E schematically illustrate such a roll forming apparatus, which is adapted to form a sectionally U-shaped long plate member. FIG. 12 is a side elevational view showing this apparatus, and FIGS. 13A to 13E are illustrative front sectional views taken along the lines A--A, B--B, C--C, D--D and E--E in FIG. 12 respectively.
The roll forming apparatus comprises a first forming part 4, a second forming part 5, a third forming part 6, a fourth forming part 7, and a fifth forming part 8. A flat plate member 3 is continuously fed into the apparatus along an arrow X shown in FIG. 12.
Referring to FIG. 13A, the first forming part 4 has a support roller 9 for supporting the lower portion of the plate member 3, and a presser roller 10 for pressing the plate member 3 from above. The plate member 3 passes through the first forming part 4 while maintaining a flat configuration.
Referring to FIG. 13B, the second forming part 5 has a support roller 11 for supporting the lower central portion of the plate member 3, a presser roll 12 for pressing the plate member 3 from above, and inclined rollers 13a and 13b for supporting lower side portions of the plate member 3. As shown in FIG. 13B, the inclined rollers 13a and 13b are located at angles slightly inclined with respect to the support roll 11. When the plate member 3 passes through the second forming part 5, both side portions of the plate member are slightly bent upwardly by the inclined rolls 13a and 13b.
Referring to FIG. 13C, the third forming part 6 comprises a support roller 14, a presser roller 15 and inclined rollers 16a and 16b. The inclined rollers 16a and 16b are larger in inclination than the inclined rollers 13a and 13b shown in FIG. 13B. Therefore, the side portions of the plate member 3 are further bent at larger angles when the same passes through the third forming part 6.
Referring to FIG. 13D, the fourth forming part 7 comprises a support roller 17, a presser roller 18 and inclined rollers 19a and 19b. The inclined rollers 19a and 19b have a larger inclination than the inclined rollers 16a and 16b shown in FIG. 13C. Therefore, the side portions of the plate 3 are further bent at larger angles when the same passes through the fourth forming part 7.
Referring to FIG. 13E, the fifth forming part 8 comprises a support roller 20, a presser roller 21, and inclined rollers 22a and 22b. The inclined rollers 22a and 22b are positioned substantially orthogonally to the support roller 20. When the plate member 3 passes through the fifth forming part 8, therefore, the side portions thereof are bent substantially at right angles to the central portion. Thus, the plate member 3 is shaped into a sectionally U-shaped long plate member along a desired configuration.
In the aforementioned forming roller apparatus, the forming parts must be spaced apart with at least constant distances, due to a restriction imposed by mechanical characteristics of the apparatus itself and due to a limitation in the strength of the object to be formed. Thus, the overall length of the apparatus is considerably increased.
Further, when the forming roller apparatus is applied to forming a sectionally U-shaped long plate member 23b shown in FIG. 11 from a flat plate member 23a, which is provided with slits 24 as shown in FIG. 10, it is impossible to smoothly bend portions located at the back of the slits 24 as viewed in the direction for feeding the plate member 23a.